The present invention relates generally to fluid control valves and, more particularly, to a piloted control valve used to deliver fluid pressure to a fluid pressure powered device.
Fluid powered devices, such as fluid powered lifts and jacks, are widely employed in the industry. Such devices are typically pneumatically or hydronically powered and include an expansible chamber or fluid powered motor for converting pressurized flow to mechanical movement. Thus, by connecting the device to a source of fluid pressure, the fluid device produces mechanical movement in one direction while, conversely, exhaustion of the fluid pressure from the fluid powered device produces mechanical movement in the opposite direction.
In order to pressurize the fluid powered device at the desired level, hereby a directional control valve is usually connected between a source of fluid pressure and the fluid powered device. The control valves are selectively operable to connect a fluid powered device with the source of the fluid pressure or, alternatively, to exhaust pressurized fluid from the fluid powered device. Such previously known values are conventionally actuated by solenoids, hand levers, push buttons, foot paddles and the like.
These previously known bi-directional control valves, however, have not proven entirely satisfactory in use. One disadvantage of the previously known bi-directional control valves is that the value member must be manually moved to a neutral closed position following actuation. Failure to do so, however, requires the reverse operation of the bidirectional control valve in order to return the fluid device to the desired position.
A still further disadvantage of many of the previously known bi-directional valves, and, particularly, solenoid actuated valves, is that while the direction of fluid flow through the valve is controllable, the flow rate is not. Consequently, with these types of previously known control valves, accurate positioning of the fluid powered device is difficult if not altogether impossible. Moreover, when an accurate position of the fluid powered device is required, the control valve must be actuated in a reiterative fashion until the desired position of the fluid device is obtained. Such a reiterative process is time-consuming in practice and, therefore, costly.
A still further disadvantage of many of the previously known manually operated bi-directional control valves is that the control valve itself must be manually unseated against a force of the fluid pressure. Consequently, when the valve is used to control high-pressure fluids forces, it is difficult for the operator to manually unseat the valve against the force of this fluid pressure. Furthermore, when the degree of actuation of the control valve is used to control the flow rate through the control valve, accurate actuation of the control valve, and thus accurate positioning of the fluid powered device, is difficult to achieve.
The present invention is an apparatus and method of actuating a fluid control valve for use with a fluid powered device of the type disposed with a fluid pressure responsive member that is axially moveable therein. In the preferred embodiment, the pressure responsive member is a pressure driven piston having a front side and a back side.
The fluid control valve connects the fluid powered device to the fluid supply source. Further, the control valve includes at least one adjustable flow control port for use in controlling the speed of operation of the fluid powered device.
The actuator assembly includes a first and second pilot valve, an in-line actuator housing and an elongated sleeve being axially slidably mounted over the in-line housing. The first and second pilot valves have inlets in communication with the fluid supply source and outlets in communication with the fluid control valve. The pilot valves are fixably attached and supported on the in-line actuator housing in an axially adjacent manner such that the first pilot valve mirrors the second pilot valve. The design of the in-line actuator housing allows for very slim diameter hosing to be attached to the inlet and outlet portions of the pilot valves whereby the pilot valves are in fluid communication with the fluid supply source, as well as the control valve.
The elongated sleeve is axially slidably mounted over the in-line actuator housing such that an opening disposed midway between its opposite ends is positioned directly over the small space between the first and second pilot valve in the in-line actuator housing. The opening in the elongated sleeve is adapted to receive a radially extending actuating member, such as an actuating plate. The actuating member is secured into position with a retaining screw that fixedly attaches to the opening. Further, the elongated sleeve is prevented from axial rotation by a guide screw located at either end of the elongated sleeve. Although the elongated sleeve is prevented from rotational movement, it is not prevented from translational movement along the axis. As such, when the elongated sleeve is moved in one axial direction, the actuator plate will engage the first pilot valve causing its operation whereby a fluid pressure necessary to actuate a first portion of the control valve is provided such that fluid pressure is introduced into the fluid powered device causing the piston to move in a first direction and, upon moving the elongated sleeve in an opposite direction, the operation of the second pilot valve provides a fluid pressure necessary to actuate a second portion of the control valve so that a fluid pressure is introduced into the fluid powered device causing the piston to move in an opposite direction.